Botany: Plant Biology and Classification

Botany Basics

• Botany is the study of living organisms called plants, as well as non-plant, non-animal organisms like microbes
• It is a scientific discipline that helps understand the vital importance of plants
• Plants initiate most food and energy chains, providing oxygen, food, and medicine

Plant Groupings

• Plant Group 1 includes photosynthetic organisms using light, H2O, and CO2 to produce organic compounds and O2
  • Ecologically defined, this group can include bacteria or even animals
  • Example: Green slugs (Elysia chlorotica) collect chloroplasts from algae (Vaucheria litorea) and use them for food production
• Plant Group 2 consists of organisms from the Plantae kingdom
  • Typically green organisms with stems and leaves
  • Multitissue, primarily terrestrial, photosynthetic eukaryotes
  • Taxonomically defined and based on evolution, allowing for organisms to be plant2 but not plant1

Parasitic Plants

• Fully parasitic plants fall into the Plant II category but may not be Plant I
  • Mycoparasites (e.g., Pterospora)
  • R parasites (e.g., Hydnora)
  • Stem parasites (e.g., Cuscuta)
  • Internal parasites (e.g., Pilostyles)
• These do not photosynthesize but have tissues, terrestrial lifestyles, and originated from photosynthetic ancestors

Levels of Organization

• Atom is the smallest unit of a chemical element
• Atoms combine chemically to form molecules
• Atoms and molecules form cells, which then form tissues
• Tissues are organized into functional organs like roots and leaves
• Organs form the body of an organism

Ecological Organization

• A population includes all members of one species in a geographic area at the same time
• A community includes populations of various organisms in a particular area interacting together
• An ecosystem is a community plus its nonliving environment
• The biosphere includes all Earth's ecosystems
• Ecology is the study of organisms' relationships to each other and their environment

Binomial System

• Biologists estimate 1.8 million extant species with millions more undiscovered
• Systematics studies organismal diversity and evolutionary relationships
• Taxonomy is a subspecialty of systematics that names and classifies organisms
• Plant Taxonomy classifies and identifies plants, requiring scientific names due to common names varying by region

Carolus Linnaeus

• In the 18th century, Carolus Linnaeus, a Swedish botanist, created a hierarchical system for naming and classifying organisms
• This system is still used today with modifications
• The Linnaean system uses taxa (singular: taxon) in a hierarchy from kingdom to species

Taxa Groupings

• The kingdom is the largest, most inclusive grouping with few shared similarities
• The species is the smallest, most exclusive grouping of similar organisms producing fertile offspring
• Closely related species are grouped in a genus

Binomial Nomenclature

• The Linnaean system uses binomial nomenclature, assigning a two-part name to each species
  • The first part is the genus, capitalized
  • The second part is the specific epithet, not capitalized
• Both names are italicized or underlined

Botanical Nomenclature

• Botanical nomenclature names plants using international rules proposed by botanists for a stable and universal system
• Essential for overcoming common name issues
• Agreement that the language should be Latin

ICBN History

• The ICBN is an agreement among botanists to follow a binomial naming system
• Before the mid-18th century, plant names were polynomials
• Linnaeus proposed rules in "Philosophia botanica" in 1751
• In 1813, A.P. de Candolle detailed rules in "Theorie elementaire de la botanique"
• In 1867, Alphonse de Candolle convened a meeting which led to the Paris code

Taxonomy

• Taxonomy, systematics, and classification have similar meanings
• Phylogenetics emphasizes the evolutionary history (phylogeny) of taxonomic groups (taxa)

Plant Taxonomy

• Plant taxonomy is a hierarchical system based on morphological and phylogenetic similarities among plants
• Classification groups plants by shared qualities and characteristics
• Nomenclature is a system of names for taxonomic groupings
• Hierarchy is a grouping system where each classification is a subset of a superior grouping

Taxonomy Ranks

• Most scientists accept seven main taxonomic levels (ranks)
  • Kingdom, phylum, class, order, family, genus, species

Phylogeny

• Phylogeny describes ancestral and evolutionary relationships among plants
• Biologists classify organisms based on evolutionary relationships
• A clade is a group of organisms with a common ancestor
• Systematists use a tree of life showing proposed evolutionary relationships among organisms

Relationships

• Relationships structured from shared characteristics, including structural, developmental, behavioral, & molecular similarities
• Classification of organisms changes with new findings, requiring the tree of life to be redrawn
• Organisms assigned to three domains and several kingdoms or clades

Prokaryotic Domain

• Bacteria have been recognized as unicellular prokaryotic cells and differ from all other organisms (except archaea)
• Microbiologist Carl Woese used molecular approaches to systematics
• Woese argued that bacteria, archaea, and eukaryotes each arose separately from a progenote

Lines of Descent

• Each primary line of descent is treated as a domain, divided into several kingdoms
• Split of prokaryotics into eubacteria (now bacteria) and archeabacteria (now archaea)
• Woese referred primarily phylogenic groupings as kingdoms
• Domain term was to refer to primarily phylogenic groupings in 1990

Biological Groupings

• There are two prokaryote groups: Bacteria and Archaea
• Two kingdoms correspond to prokaryotic domains
  • Kingdom Archaea → Domain Archaea
  • Kingdom Bacteria → Domain Bacteria
• Viruses are non-living pieces of DNA or RNA out of living organism cells
• Viruses can evolve despite not being living

Eukarya

• The remaining kingdoms and groups are assigned to the domain Eukarya
• Main 4 kingdoms: Protists (e.g., algae, slime molds, amoebas, & ciliates) are unicellular, colonial, or simple multicellular eukaryotes Word protist (Greek for "the very first,") conveys that protists were the first eukaryotes to evolve
• Protists are primarily aquatic organisms with diverse body forms, types of reproduction, modes of nutrition, & lifestyles
• Some protists perform photosynthesis
• Plants are complex multicellular photosynthetic organisms

Plant Groups

• Kingdom Plantae includes nonvascular (mosses) & vascular plants (ferns, conifers, & flowering plants)
  • The vascular plants have tissues specialized for transporting materials
• Most plants adapt to terrestrial environments
  • Fungi : yeasts, mildews, molds, & mushrooms (do not photosynthesize)
  • Fungi secrete digestive enzymes into food and absorb the predigested food
• Animalia: multicellular heterotrophs with cell & tissue specialization and body organization

Taxa Names

• The plant kingdom is divided into categories that differ in rank & size
• Rank: the level in a taxonomic hierarchy -Ranks compare taxonomic groups from major groups -Taxonomic ranks (species, genus, family order etc.), each rank subsumes a number of less general categories
  • Species: The basic unit in plant classification is species
  • A species is a single type of living organisms.
  • Genus: is a group of related species
• Rank example: The genus Rosa is made up of related rose species that differ in their vegetative characters

Family names

• Family: a group of closely related genera
  • The scientific name of a family ends in -aceae, such that Rose family is Rosaceae
• Order: a group of related families ending in -ales
  • Example: The rose order is Rosales

Related Groupings

• Orders are grouped into classes, & classes into phyla
• Phyla can be assigned to kingdoms, and kingdoms are grouped in domains
• In addition to the seven ranks, taxonomy uses intermediate ranks when the taxonomic structure is too complicated

Name Endings

• Exceptions: Some of the families do not end with aceae, so they are provided with alternative names as: Cruciferae – Brassicaceae Compositae – Asteraceae Graminae – Poaceae Guttiferae – Clusiaceae Leguminosae – Fabaceae Palmae – Arecaceae Umbelliferae – Apiaceae

Binomial System Rules

• Binomial System Generic Name Rules:
  • Generic name is the first word (capitalized letter)
  • Always a singular noun, coined from different sources
  • honors a botanist: e.g., Linnea for Linnaeus, Adansonia for Michel Adanson
  • expresses features of a plant: e.g.; Pterospermum (winged seeds)
  • is named after a place: e.g., Araucaria (Arauco province of Chile), Cassia (Mountain cassia from N.Syria)

Epithet Rules

• Specific Epithet (2nd word) rules:
  • First small letter and is an adjective
  • Source: description of a plant:
    • Example: A- alba (white), nigra (black) the color of the plant or plant part, , or B- the habitat of the plant aquatic (in water) arvensis (in fields)
  • honors some botanist: eg Vanda roxburghii
  • is descriptive with adjectives: e.g., cordifolia (heart-shaped leaves)

Plant Kingdom

• Plant Kingdom – Plantae - includes all the plants - These organisms are eukaryotic, multicellular & autotrophic
• Plant cells contain a rigid cell wall
• Plants have chloroplast and chlorophyll pigment for photosynthesis

Plantae Classification

• Plants 2 (kingdom Plantae) contain > 300,000 species that are divided into multiple subgroups
• Plant kingdom - further classified into subgroups: based on the following criteria: - presence or absence of a well-differentiated plant body -Root, Stem and Leaves - presence or absence of a vascular system for the transportation of water & other substances -Phloem and Xylem - seed formation or the seeds - if the seeds are naked or enclosed in a fruit

Cryptogams vs Phanerogams

• A.W. Eichler introduced a phylogenetic system of classification in 1883 and divided the plant kingdom into Cryptogams & Phanerogams
• Cryptogams: less evolved seedless plants that reproduce by the production of spores.
• Phanerogams: highly evolved plants that bear flowers & seeds for reproduction.

Plant Kingdom Classification

• The plant kingdom has been classified into Cryptogams and Phanerogams:
• Cryptogams (spores)
  • Thallophyta: Primitive plants with undifferentiated bodies but no stem roots & leaves
  • Bryophyta: Small, non-vascular plants that prefer moist environments
  • Pteridophyta: Spore-dispersing vascular plants
  • Phanerogams - Gymnosperms: plant body & vascular tissues in a welldifferentiated way - bear naked seeds (not in a fruit) - Some of the common examples of gymnosperms include things like Cycas, Pinus, Ephedra, etc. - Conifers have cones rather than flowers: pollinated by wind -Angiosperms - plants are seed-bearing vascular plants with a welldifferentiated plant body and seeds enclosed in fruits. - Vary in size (Wolffia ≈ 0.1 cm to Eucalyptus ≈ 100 m tall) - Divided into monocotyledons (Magnoliopsida) & dicotyledons (Liliopsida) according to the number of cotyledons present in the seeds. - Examples: mango, rose, tomato, onion, wheat, maize, etc.

Life and Chemistry

• Styles of Life and Basic Chemistry: - Life obtains energy in a few different ways: - from sunlight - from chemical reactions with inorganic matter - from breaking organic molecules into inorganic molecules (typically carbon dioxide and water) Modes of Nutrition:

Autotrophic Nutrition

• Plants can be divided into two groups on the basis of their mode of nutrition or autotrophic nutrition - organic compounds are manufactured from available inorganic raw materials - Two autotrophic subtypes based on energy sources - Phototrophic nutrition example: Green Plants) make organic molecules -Photosynthetic Bacteria use light energy as a source, through photosynthesis -Photosynthetic bacteria: synthesize carbohydrate food without chlorophyll

Chemotrophic Nutrition

• Chemotrophic Nutrition (aka chemosynthesis) - autotrophic nutrition: - organic molecules are manufactured (energy produced by the oxidation of inorganic substances like ammonia, nitrates, nitrites, ferrous ions

Heterotrophic

• Heterotrophic nutrition in plants
• Plants that not capable of manufacturing the own organic molecules (either entirely or partially) depend for these organic molecules
• Classification of heterotrophic plants: - Parasitic plants or parasites depend: depend on living plants and animals -Saprophytic plants or saprophytes depend: depend on dead or rotten organic remains of plants or animals. -Break up complex dead food material into simple compounds for their growth and development
• Special Mode of Nutrition -Carnivorous or Insectivorous plants called Carnivorous plants: Plants with insects & small birds
• This is a special of nutrition - partially autotrophic & partially heterotrophic, they -possess green pigments & manufacture CHO - cannot synthesize nitrogenous compounds and proteins - For their nitrogen requirement